Stimulus overselectivity is a term used to describe a phenomenon whereby a person focuses on only one aspect of an object or environment while ignoring other aspects. Many autistic individuals appear to have this 'tunnel vision.' This phenomenon was first described in 1971 by Lovaas, Schreibman, Koegel and Rehm at U.C.L.A.

The literary works on autism contain numerous stories of how autistic children 'tune in' to an object or a single aspect of an object while blocking out other parts of their environment. Some professionals argue that this is the reason why parents often suspect their child of being deaf. Parents sometimes test their child's hearing by banging pots and pans behind their child's back, and the child fails to react to this 'unexpected' sound. However, in different situations, it is obvious that these children can hear, such as the case when child is quickly nearby when a parent opens a candy wrapper.

Dr. Lovaas et. al first tested this concept of stimulus overselectivity in autistic children by instructing each child to press a lever as soon as three different stimuli were presented at the same time (i.e., a light, a sound, and a touch). When he/she pressed the lever, the child was rewarded with a piece of candy. Later, in the testing condition, the three aspects of the complex stimulus were presented individually. The results showed that the children pressed the lever when only one of the three stimuli were presented. For example, a child would press the lever when a light was presented, but he/she did not press the lever when the sound was presented alone nor when the touch was presented alone. Dr. Lovaas and his colleagues argued that during the initial learning phase, the autistic child attended to only one of the three aspects of the complex stimulus rather than all three aspects.

The idea of responding to only one of many aspects or dimensions of an object may make it difficult for the autistic child to learn about his/her world. For example, if a child is being taught to differentiate between a fork and a spoon, the child may attend or focus on the color (a very salient aspect) rather than the shape. In this case, the child will experience much difficulty when trying to decide which utensil to use.

We do not know why autistic individuals have this tunnel vision. One theory states that these individuals are born with 'too much' concentration; and as a result, it is very difficult for them to expand or widen their attention span. Another theory states that these individuals cannot process or attend to the environment as a whole because it may become overwhelming, i.e., lead to overarousal. As a result, they may try to simplify their life by focusing on only a small part of their worid.

Implications. Since it appears that many autistic individuals exhibit stimulus overselectivity, it is important to help them direct their attention to relevant aspects of an object or the environment. For example, when teaching an autistic child to select an apple from a bag of apples and oranges, the child should be instructed to attend to color and texture. In contrast, when teaching the child to find the family car in a parking lot, the child should direct his/her attention to the color and shape.